black sea
by blurrywrote
Summary: a.n: title from natasha blume's "black sea" / so. how's about a spy au / the entire idea of this fic was inspired by kami's amazing art @kamilecn ! / btw nothing is gonna go in any order. just snippets here and there. but there's plot, i promise.
1. formal wear & magic

" _Fancy_ meeting you here."

A grunt was her only response, face down and hand lightly rubbing her nose from the surprise impact against the other's chest, and though she couldn't _see_ him she could very well _feel_ that crooked smirk of his. How a skull could mend to smiling and blinking is beyond her comprehension, but the woman has seen stranger things – talking skeletons was just one of the things she had the privilege of getting used to.

And what a _lovely privilege_ that was.

Frisk huffed, the air making her bangs fly up and away from her eyes as she leaned on the wall, trying to press further away from Sans as possible. The bump to her nose felt now like an itch, minor against the continuing throbbing of her ankle, and she held in a hiss when testing out if it can manage her weight. It didn't, and now she had to keep her leg raised somewhat in this small space, knee bent and brushing against the skeleton's dress pants.

If she weren't so annoyed by the situation she would have complimented him on his wear.

"Nice dress."

Ah. Well. He beat her to it.

The woman slid a bit of her hair behind an ear and kept her gaze toward their only exit. "Thank you. Do you think you can open that door?"

"Mm. Nope."

She suppressed a glare and kept her tone even. "Why not?"

He tapped the heels of his dark shoes against it. "Sturdy and infused with magic. Thought you would've known that much."

"Can't you just – Oh, I don't know. Blast it open? Teleport to the other side?"

He raised a brow. Well, the rim of his eye socket raised in a way that a brow might have. If he had one. Which he didn't. And yet that movement was still infuriating without skin or hair.

Frisk was pretty sure he didn't even need to breathe, and yet his chest rose and fell as hers did. The top two buttons of his black shirt were undone. ( Why was that even a bother? ) She kept her eyes on the door.

"Honey–" _Oh he did not_ _just 'honey' her_ "–as much as I'd like to get out of here, and I very much do, this is a pretty strong barrier we're dealing with here."

"A barrier," she flatly said, patience running as thin as the _very non-existent space_ between them. "On a broom closet."

"Yep. Thank your sister for that."

At the mention of Chara, Frisk's attitude shifted. The creases on her forehead that started to arrange into a small frown were smoothed over and her eyes fell.

 _Damn, she was so close._ So close to reaching her, basically touched ( well, more _deflected_ ) her sibling's hands but they slipped away again. Why? Why couldn't she reach her? This had been one of her opportunities to talk to her and they spent most of it running instead. Whatever Chara was planning, whatever it was that was making her cause all this ruckus, Frisk just hoped it was worth it. She was in enough trouble as it is, running from police and staying in hiding – and the moments she wasn't hiding she was brewing up rather suspicious behavior. Frisk didn't understand it, but she refused to believe her sister was a bad person.

Sans saw it differently. In fact, they might as well be in very separate teams, seeing as he wanted to bring Chara in for what she _supposedly_ did. There was no convincing him. He truly thought...

That Chara _killed_...

There was just no way. Frisk refused to believe any of it. Sure, her sister had certain _unlikable mannerisms_ , but murder?

"So," Sans' voice brought her back, and she blinked up at him, almost taken aback by just _how close_ they've been. Though of course she had _absolutely no room_ to actually take a step back. "What's with the stick?"

Frisk raised her hand, looking down at the object in question before sighing and dropping it. She felt the beginnings of a blush start to rise on her cheeks. "Nothing."

"Nothing?"

She could hear his laughter in that word alone. More than that, she could hear the very essence of his _soul_ – skeleton monsters had no heartbeat, but if one were to pay attention, if they were close enough...

Eyes restrained from rolling too far. "I might have made a small mistake."

Sans raised his bony hand to his chest in mocked surprise. "The perfect Frisk Dreemurr? Making a _mistake?_ "

Her cheeks were certainly burning now. "Oh _shut it_. Before I pick up the stick and give it some good use."

"Like blasting the door via wizardry?" His grin widened _and could very well much eat shit for all she cared_ as he flicked his wrist, his index and thumb digits pinched together.

"I never would have guessed Chara's magic could surpass your own, Serif."

The comment didn't seem to phase him as much as she wanted to. He shrugged, but at least that grin lessened to a degree she could tolerate. "Can't say you two weren't taught by the best."

Toriel came to mind, and so did her phone and she swiftly reached down her front to retrieve said device. Only to come up empty. Well, that's great. Not like it would have came in handy or anything.

Sans cleared his throat, most likely having seen her shove her hand between her breasts ( though it's not like he hasn't seen _that_ before and in a _much heated fashion_ ). "Looking for something darling?"

His voice certainly should _not_ be making her relax, but it always had that effect. "Phone. Have one on you?"

"I think the magic would cut the signal anyway. Let's just wait 'til it wears off. Shouldn't be too hard, being this close."

 _What a charmer._ Frisk opened her mouth to say something, even straighten up, at least make _him_ be the one to press away – though she could hardly blame him for being tall, his back already bent forward and his skull dangerously close to touch her head – but when she put her foot down she grimaced and pulled it right back up.

Sans noticed, and his usual comic charade came to a stop, voice drooping lower as his glowing pupil inspected her. "You alright?"

"Fine."

"Obviously." He glanced at her raised foot before meeting her eyes again. "May I?"

She sighed, knowing that she might as well let him help. This wouldn't be the first ( or last ) time he'll touch her. "It really is nothing. Just sprained."

He hummed in response, bone meeting skin as he swept his fingers over the bruising area with a gentleness that brought up some rather _unneeded_ memories. "High heels, every woman's Achilles'... _heel_."

"I can still grab that stick."

Sans smiled a bit wider, but he said no more, hand now glowing along with his only working eye. The one eye that Chara spared that night.

Shifting, Frisk had to grab on to his the fabric of his shirt while he continued to heal her ankle. He didn't mention it, which she appreciated, and she began to let her shoulders slump, trying to appease toward the calming side of all that's happened that night.

But she couldn't. Chara was still well in her mind, and it bothered her. It bothered her to the moon and back that she didn't know what was going on – why her sister didn't just _tell_ her. It wouldn't be because Chara was hiding something, they told each other everything since the very start. It must be for protection. It has to be. But Frisk can handle her own, they've been trained as equals.

Which is why Frisk was the one in a broom closet with her ex and a broken foot while Chara was off free doing... whatever.

"You didn't give me a real answer."

"Hmm?"

"The stick." He was _still_ on about that? Probably won't let her put that one down either. "Were you _always_ carrying it around?"

He was done healing her and he let her go, the absence of his touch both a relief and a disappointment. Frisk put her foot down and tested her weight on it slowly, breathing out softly in gratitude as the pain dulled. It wasn't completely gone, but Sans was never meant to be a healer anyway. Still, it was way better than nothing.

When they moved again she took note that she was still the one with her back against the wall, Sans straightening out as much as he could with both hands on said wall behind her, as if she needed to feel more caged in as it is. She couldn't _not_ stare back at him this time, and she would make sure to thank Toriel for teaching them a breathing exercise that controlled the beating of one's heart. Though not much could be said for the warmth on her cheeks.

"I had a... _talk_ with my sister."

"Ever the so chatty one, she is." He was joking, but she could feel him tense up.

"She didn't hurt me–"

"That much."

"It was mostly the heel, alright?" She became defensive quickly, but not for her part. This was why they had to break it off. Whenever it came to her sister, they always started to fight. She really hoped it wouldn't happen again, but here they are, with no choice but to head on.

"Sure."

He was still not convinced, but at least he didn't take it further. Frisk won't thank him for that. Not as long as he was still after Chara.

"I fell–"

"Or _she_ made you fall."

"...dropped the knife–"

"You were conversing with _knives_."

"She _kicked it away_ when she had the chance and then ran off. I was in a hurry so I just... grabbed the first thing that came up. I tried to go after her, but... Anyways, we both ended up here."

"Wow, that is... something."

"Well, now you know. About the stick."

He said nothing, they both stayed still for a moment, but their unwavering gazes locked in a silent battle that neither back away from. Eventually, Sans sighed, the air tickled her bangs, and he leaned even yet more forward.

Frisk froze as his elbows also touched the wall, arms still encasing her as he softly bumped his skull against her head. She didn't think any breathing technique could help her at that point, ribs just barely keeping her heart from leaping out. The blush was sure to cover most of her face now, along with her ears and down to her neck.

The female spy had been in similar positions before, with him and others ( though those were not taken seriously, and were strictly kept professional ), but with him it was... it would always be different.

It made her ache.

"I'm sorry."

 _Really_ ache.

She was surprised her voice worked steadily even as it felt like the air was stuck in her throat. "For what?"

When he had spoken, his voice was low and gentle, and it sent small goosebumps through her skin, starting from her shoulders. It was unlike him to point it out and tease her.

"Just how things are right now. How they're turning out... and what happened–"

"Everyone is still in shock, no one could have seen it coming nor control it. I... am not angry at you. _I'm_ sorry. For how I've been treating you. I just..."

"I know. You care about her."

He moved away then, saving her from suspension, and when he looked into her gaze again it sent another shiver down her spine – and not like the previous ones. His glowing eye was gone and when he spoke his voice was still low, but hinted _warning_.

"But someone _I_ cared about is now gone. No one was there to see it when it happened, but all evidence points to _her_. Whether you agree with me or not, Frisk, I'll be hunting her down. You just pray that you can reach her before I can."

The door suddenly opened, alarmed voices rushing in with yellow light from the hall, people looking in to see a lone woman in a closet, looking out before her like someone just shattered her soul.


	2. eyes?

Being a monster in public places and events, especially one as big and expensive such as this one, meant having security grind you from the ass up and it never failed to piss Sans off. But while he kept nonchalant, Undyne was actually pretty vocal about it.

The skeleton monster kept his hands behind his head as a gruff guard patted him down and inspected his coat, and the whole time he stayed quiet beside his "date" for the night, who did a poor job of concealing her frustration, practically _flashing_ in golden scleras as she muttered yet another swear to the woman security who currently patted her waistline. When they were done being inspected they were allowed entrance, and Undyne snatched back her purse before briskly strutting away (well, if strutting meant almost breaking her heel in those high shoes then she did a pretty good job).

Sans still said nothing as he began to roll up his shirt's sleeves, and when catching up to the female monster he did a show of covering her shoulders with his coat, which he had to take off at the entrance anyway. Undyne looked at him questionably as he finished baring his forearms, the bone thicker and denser than a regular human's skeleton and it was as much of a pain reminding people that his structure is _supposed_ to be different from their anatomy as it was being man-handled by one who smelled of cheap cologne.

When Undyne knew he wasn't going to even try to amuse her with an answer just by staring at him, she narrowed her eyes slightly, pupils thinning to dangerous slits. " _What?_ Do I look as horrible as I feel?"

His grin grew wider. Just a bit. "'course not, but it's a cold night."

Her stare was as flat as the polished marble floor but her hand held the front of the coat to shrug it closer. It was a good thing it was made by monster standards, the material able to withstand the minimum blasts of magic, and sharp scales for this instance.

Sans had to scratch his jaw to hide his chuckle. "I was also worried that if you bumped into a poor little human then your bare shoulders might have cut their skin right off."

"Darn, and that was _exactly_ what I wanted to happen."

She tried to scowl, at least keep the annoyed frown to stay etched above her curved eyes, but there was no helping just how amusing that might have been – everyone thought that the security was a waste of time and ineffective if monsters brandished sharp teeth, claws, and obviously _fucking_ _magic_ that could prove just as lethal as a firearm. Undyne had to snort, rolling her eyes, then slid her arms into the coat's sleeves. It actually looked pretty nice along with her light blouse and black dress pants.

"Is that your way of telling me I look sharp?"

Sans faked a wince. "I totally missed that opportunity, didn't I?"

"Oh fuck off, you probably thought of it before we even got here."

"Guilty. Now, let's try to look like we're enjoying the night together."

Undyne curled her lip. "As much as I like getting picked for a job, why wasn't someone else, like Muffet, picked for this?"

"She might have made for a nice choice, and definitely would have been sweeter, but I find her hands to be a bit clingy."

"I counted two puns in there, one more and you're out. Unless you want me to show you how I'd rather be using these stupid slippers."

He grabbed her hand and lifted it as he was going to kiss the blue scales atop her knuckles. "My, my, at least wait until we're in a bedroom."

An eyebrow shot upward and that was his only warning before she pinched one of his phalanges, successful in breaking away from his suggestive hold, and the grip between her fingers was enough to convince him that she could shatter his wrist, his whole arm, if she wanted to. He believed it, since magically he was the strongest one, but _physically_... he was good as fucked, not that he didn't know how to fight, but Undyne's abilities called for more training in hand-to-hand combat than he did.

Sans chuckled, though normally if they weren't surrounded by so many people his skull might have condensed a sweat. Jeez, her glare could dust a monster where they stand.

"There's a lot of things wrong with that, starting with how gay I am."

Undyne could be pretty hilarious when she wanted to.

Fortunately she wasn't going to commit homicide in front of so many witnesses and she let go, sighing as she collected her long red hair from beneath his coat and having it cascade down her back. The fiery color of her hair along with the soft shimmering navy blue of her skin had human eyes sway in her direction. Of course, monsters were always being stared at around these parts of the city. It wasn't exactly the most friendliest of places, and people weren't used to seeing their kind flaunt around. And while Sans was also a victim of a gawk or two from shock (okay, more than just a few), there was also no doubting that someone as _bare-boned_ as he was could make the skin of a human flush. It's happened before.

He's felt it before.

Focusing, Sans placed one hand in his pocket while the other pressed against the back of Undyne's shoulders and guided her toward a further table. He kept quiet as he observed the huge room, area filled with fancy suits and skirts of all caliber, the music playing softly somewhere near the dancing area. It would have provided as a time for a nice distraction, if it wasn't how this whole getup was the perfect way for certain dangerous people to meet. And there was one in particular that Sans very much wanted to talk to.

Undyne sensed his attitude shift to business and she prompted a quiet understanding to his thoughts, her own gaze traveling across the room carefully. When they reached a certain distance their bodies faced each other closely, the female monster sliding her purse between them as they still looked to everywhere but each other. A few heads turned their way in curiosity. Monster couples were a fascination it seemed.

"I'll check outside," he said softly, reaching into his coat that the other still wore, his hands grabbing on to a cigar and a lighter. The movement was enough to get those prying stares away from them, as if they were intruding in something private. "The garden looks promising."

"I'll take the main halls then." Undyne then turned slightly, voice getting higher so they wouldn't have to murmur to one another so much, and she took out a small round mirror from her bag. It looked to be Mettaton's, as surely Undyne wouldn't be caught dead with all this product. "I'll just go powder my nonexistent nose."

He placed the cigar in his mouth. "Take your time, _hon_."

She looked like she was going to retort back sharply when something caught her attention behind him. The redhead then promptly looked back to Sans as casually as she could but he noticed that surprised look on her face, and he turned his head to see what it could be.

Sans could feel his soul stop when he saw _her_ there, a light seeming to catch her brown hair and soft eyes and plump lips that glistened with a tempting gloss – she looked so damn beautiful it was unfair. He felt his jaw slack and he had to catch the cigar between his fingers, and he found himself putting it away in his pockets; he remembers that she didn't much like the smell of smoke.

 _Never mind that now_. What the hell was Frisk even doing here?

Actually no. That was obvious, she was here for the same thing. For a completely different reason, he was sure, and he could feel the fluttering and consistent thrum of her determination from across the room. It was almost like it called to him, and he had to shut his vision with a hand rubbing down his face, the sound of bones sliding against each other helping him to snap _somewhat_ out of it.

Jesus H. Christ that dress was _distracting_. He sure as hell didn't come prepared for this.

Undyne was amused. "You think your ex will mind our little date?"

"Go do your job."

She scoffed then, squeezing his shoulder as she began to leave. "Oh I will. Make sure you do _yours_."

"You know I don't slack off during work."

"Uh-huh."

She sounded as unconvinced as he felt, but the dread crawling up his spine couldn't hold a candle to the resonate of his soul reaching out to at least brush the unmistakably vibrant red pulse of Frisk's. If he had a stomach he supposed he could call this butterflies. Now he _really_ needed that cigar. Or a drink. Maybe two.

Frisk hadn't noticed he was there, in fact she looked pretty focused in finding that certain someone; which Sans himself should be doing and he blamed her pettily for making it difficult. Taking in a deep breath, he fiddled with the contents in his pockets as he took to walk outside, needing to drag his gaze away from... the lovely scenery.

He took to blending in with the darker corners of the garden, lights hanging from trees and the huge fountain in the middle providing a soft golden light, the architect having the ripples of water shining on its surface. It made for a pretty view, and the flowers were a nice touch, and yet that didn't matter. It wasn't really supposed to matter either way, and he is supposed to be taking this time to search, and he isn't supposed to be getting this frustrated and neither should he be waiting (hoping?) to see Frisk right around whenever he hears a clack of footsteps approaching.

Undyne was right in suspecting he wouldn't be concentrating to his fullest – especially counting the many times that she had walked in on his and Frisk's _less professional_ moments. None of their coworkers gave a damn about their (now nonexistent) relationship but the pair tended to forget themselves and their surroundings from time to time. Frisk always did try to be more careful, and Sans was uncaring over those sorts of things but he did respect her want of privacy. Undyne just had the bad luck of finding them being busy; twice had she seen them in positions that Sans would call chaste but it had made the female monster swear and blush as red as her hair. She was in no way innocent, but upon seeing others display affection she was sure to feel some form of secondhand embarrassment.

The last time Undyne had walked in on them things were intense. Of course anything Frisk does passionately would be vigorous, and their break up was no exception. Specifically, the reason behind said separation was what drove both of them on opposite sides. Sans was the type to not want to linger on arguments, but...

Needless to say, Frisk was the one to leave the room that time while Undyne stood still by the door in shock. He had disappeared the moment after, not wanting to discuss with anyone on what happened. Thinking of it now made him want to hit one of the pillars.

Growling, he decided to might as well use this spring of tense magic to good use, and with a jolt he realized Frisk's energy was nearby, danger of contacting the force of his own. He cloaked himself quickly, knowing that if he teleported out of there she would easily figure out that he was present. Sans took a fleeting second to look at the garden once more before deciding that, _whatever_ , he wasn't going to get any progress like this anyways, so he took to heading back inside.

She was rejecting someone's offer to dance when he came in (figures she'd come do this alone), and though he might have felt like intervening he already knew what Frisk was capable of: that glare was perfected down to the very downturn of her full lips, and the ire behind her warm eyes – now hot and burning and dark – was enough to let the other know that she was not in the mood for negotiating in any further discussion. He felt a little pity for the poor guy, seeing as he was the victim of the same glare on occasion when he first met her. Well, it wasn't really _her_ doing the glare, but her sister could create the same affect along with the promise that she _will_ hurt him. Toriel sure did have quite the influence on them.

Frisk was still searching, her strong will of being able to find her older sibling fueling Sans' objective further, as well as drowning it. He hated the circumstances now circling them like a plague and if things were a bit different then he would have called it quits and left her to it, maybe help her. But he won't do that, he _can't_.

Moping wasn't going to help anything. Finally forming a new and more practical solution, he opted to follow Frisk's flow of magic, making sure he was still well concealed in the meantime. It was a good strategy to search for Chara like this, finding even a trace of her soul lingering anywhere could lead them to _some_ clue, but it wasn't as effective for Sans nor anyone for that matter to use except for Frisk, and maybe Toriel; souls had to be linked in order to be able to find the other. That's why he found it so easy to recognize Frisk's soul, seeing as they had bonded. The fact that she hadn't noticed him yet stung a little, but all her focus was set on finding her sister anyway so he didn't take it too much to (his hypothetical) heart. Or tried to. He had to remind himself that he shouldn't _want_ to have her see him, but he was never good at keeping to his word.

Tracing Frisk's magic was easy now that he was able to spare a glance at her direction every now and then while she did the work for him, his hand idly holding a glass of white wine. He found himself murmuring a soft encouragement when the woman hesitated to continue, already having reached all of the ballroom and the garden. Doubt began to show as she grasped her thumb and he knew she was keeping from biting into the nail – it was a habit of hers that he found adorable, though right now he really wanted to do more than just watch from the sidelines as her gaze became distant. She already drained maybe too much energy; humans weren't strong magic users to begin with, and he admired just how much she pushed past those limits. Frisk was always breaking and bending the rules to her whim.

Just when he thought she was going to give in, she let out one last sudden pulse that, if attainable, could have been able to shake the very walls. Her eyes snapped to one sole direction and her pace became steady and confident.

 _Bingo_. She's found Chara.

"Good job, honey," he breathed quietly, soon following after.

He could feel his left eye begin to burn, the absent feeling on his right still foreign to his skull. If not for his brother, if Chara was _really_ innocent for that as Frisk so adamantly believed, then he could at least make her pay for his damn eye.

* * *

The woman's bathroom from the left wing was now put out of order, its stalls crashed and a few sinks broken. Some water was leaking on to the floor and a whole toilet seat had been removed from its place on the ground and tossed to the other side of the room. Undyne was guilty of that. Not _all_ of the damage was for her part and she would chew anyone's head off who thought so; it wasn't exactly ideal to get ambushed.

She should have known what was coming, the room was a bit too quiet, _especially_ for being a woman's restroom. Men in suits don't really belong in there either.

Undyne hisses while forcing her hand to stay under the cool running water of a still-working faucet, the torn and bloodied knuckles giving more of a sting than she was used to. The skin on those guys was oddly hard and would have caused more trouble if the female monster wasn't covered in scales. Admittedly she had to use some magic, but even the best of their kind had to use certain measures when surrounded and outnumbered.

Her golden eyes gave an impression of sparks as she jerked her head to one of the men crawling toward the door, she snorted and barely flicked her wrist as a blue beam (shaped to her usually preferred spear) shot out and pierced through the man's shoulder and into the wall behind him, pinning him accurately with a satisfyingly pained cry. Undyne examines the others, still tied and bundled together in a heap of scrapes and bruises, for whatever damage they had landed on her she had unleashed tenfold on each of them.

Mettaton's purse was pretty useful now, having helped to carry more than just some flimsy mirror and eyeliner – reaching inside, she pulled out several monster candies and threw one into her mouth while slowly making her way toward the man who tried to get away. A few of them have given pretty good hits and she'd have to apologize to Sans later when giving back his coat. It wasn't torn, the men weren't _that_ good, but it was pretty stained. She also might have used it to suffocate someone. Not a huge deal.

She grabbed on to the solid beam of her magic and the man stopped struggling as soon as she placed her foot on his thigh, dangerously near his groin. This spear in particular wasn't made to do an awful lot of harm, even if it was jammed right through the guy's body it wouldn't be enough to make him bleed; it was a carefully tuned magic, and Undyne still had to work on it. She was sure it at least cast a sense of burning, so not at all a pleasant sensation. Well, not like these people deserved any more mercy.

"Are any of you dicks gonna speak up and tell me what your deal is, or will we do this the hard way?"

No one spoke up, but one was brave enough to spit on the ground, further staining the tiled floor. Classy.

Undyne rubbed the back of her neck, craning it a little. "Fine by me. But first, I'm gonna need you to open your eyes when I'm talking to you."

It was bad enough that they all kept it closed while fighting, and now it was just rude. She bent down to forcefully open this one man's eye herself, but once she was met with an empty eye socket she flinched and whirled back in shock. Her emotional stupor caused the beam to disappear and the man's lips started to rise unnaturally, and though he didn't make a move to get up she still backed away.

The female monster felt sick as the other men also opened their eyes, all hollow, and with wide smiles that stretched beyond their cheeks and to their ears. She would have choked on her candy if it wasn't for how stiff frozen she was.

"Eyes?" they all mocked, inquiring in unison. As if they weren't already creepy enough...

Undyne bit into her candy then, feeling like she's had enough and she _won't_ show that she is intimidated in the least. Gritting her sharp teeth, fangs displayed over her lips as she growled, she sent several new beams to the group of men tied together, the crunch of splintered bone echoing through the white room. This left only one of them to deal with. If they weren't so demonic, then she would have obviously spared them, but seeing as they're _not human_ she wouldn't hesitate to get rid of them.

The man who had been pinned kept sitting on the ground, that stupid creepy smile plastered on his face as if someone had stapled it that way. He wasn't at all perturbed at the fact that she just skewered all his buddies skulls in.

Undyne gathered her purse to her side and summoned another spear, pressing it underneath the man's chin. "I don't need all of you to tell me what the fuck is going on."

"Our job is done here."

Oh she did not like the sound of that.

"All we needed was to keep you separated from that other guy." It was then that his eyes started filling up, black ooze sliding down his taut skin, the substance running easily like tears. His body shook and he slumped further down, as if something that took possession of his body had suddenly leaped out and left, and now there was only a husk. "Good luck, _monster_. You and your friends will need it."

He died mid-laughter, Undyne's magic announcing itself from inside his body and making its way out. The thick black substance continued to drip down the male's chin, though strangely his wounds bled the natural and normal red that humans held. Disgusting, but interesting.

Undyne muttered as she began to signal for Sans – his magic would be useful to get these bodies cleared out of the room, maybe bring them in for examination. "Alphys should see this..."

"Sorry, but _you_ won't be able to see as much after this."

A sharp pain stabbed the back of her skull before she was able to turn and face the abrupt voice. The air began to thin and her vision turned dark, but she thinks, maybe, that she was able to feel a familiar sense of Human Determination.

* * *

He stopped in his tracks as soon as he felt Undyne reaching out to him, except the signal cut off soon after and he did not like to think of the various reasons why. He hopes it was a simple mistake. Frisk was still nearby and he hesitated, wanting to still follow her scent but now anxious as to what Undyne could have needed. Both women were exceptionally skilled, each their own warrior, but they would still need help.

Sans sighed, knowing that his emotions were very much involved and leading to take him with Frisk, but checking on his partner was the logical response. If anything, he could try to get information from Toriel, they still kept in contact from time to time. And if Undyne was really in trouble then Chara became a secondary problem.

He was a patient man, but this little game of sidetracking was beginning to get infuriating.

When he took another corridor he knew he should have teleported straight to Undyne the moment he sensed her distress. At the end of the hallway stood Chara, casually swinging a vile filled with a glowing blue aura as she kept her back to him. He immediately knew what it was she was holding and he felt his hands tighten to a fist – she was using his eye, _she could manipulate his magic_.

The human turned her head, strands of her short hair brushing over her curved shoulder, and caught his stare. He expected her to smile, wink, _something_ to further enrage him but all she did was walk. A very tempting invitation for a trap, and he was going to willingly step into it if it meant getting some answers.

Remembering Frisk though he began to hesitate again. He couldn't feel her anymore, and his soul longed to stretch out, have the satisfaction of knowing she was still okay.

"Why are you standing idly like an idiot?"

Sans was only momentarily surprised at seeing Chara across from him, closer and against the wall with her hands calmly kept behind her back. Her red eyes always did a good job of reading him carefully; sometimes she was too good for his liking.

His voice remained aloof, the same old dance they've always had, even before this mess began. "Just what are you planning, little princess?"

That usually peeved her off, but she was as unreadable as he was. "No time for chatting, I'm afraid. You should hurry and help your friend. Cutting through scales is messier than bone."

He became still, the light from his sockets now gone. "What did–"

"Exactly what you think I'm doing, genius."

She swung the vial again, and he felt cold and bare and he could just _kill her_ right now, hurt her like _she_ did to _him_ –

But he could hear Frisk already, pleading, consoling her sister, asking for a chance. He could color the desperation on her expression so perfectly, etch it into delicate ice. And he knew he wouldn't be able to do it.

In the moment, it would feel good, _very good_ , to bash Chara's body through several of these walls, but he wouldn't be able to withstand the looks that Frisk would give him if she knew.

 _That woman..._

Sans made his chest move, mimicry of habitual breathing, and started walking to where Chara was trying to lead him. "You keep that eye safe for me while I go fix your mess."

There was a small smile there, a corner of her mouth lifting too innocently. "I'll keep them both safe. But you two are going to be in a load of danger if you're caught out here."

 _Both_ eyes? Shit, did she...? "Undyne and I know the risks."

She was chuckling. "I wasn't talking about Undyne."

He wasn't allowed a moment to react when he heard a flurry of rushed footsteps approaching, and suddenly Chara was directly in front of him – then phased right through him. _An illusion_ , he was right to suspect, but he was still knocked back by yet another body that was following after Chara's image.

And of course it had to be Frisk. She snapped her head back while adorning a frown, mouth open as if ready for accusation but instead turned to surprise, and she blinked.

"Sans?"

The monster almost swore out loud, but all he could manage to do was stare back at her eyes, his hands unconsciously holding on to her arms to steady her.

He felt a familiar tug to his soul, the sense of his magic being put to use _without his doing_ hummed in the air and it was then that he realized a small closet door opening behind Frisk. Chara wouldn't...

Oh but she was, and she did. And she _laughed_ , too. Bidding them a good time in the claustrophobic-inducing room after having slammed their souls not-too-gently into a wall, poor Frisk getting more of the blunt impact of the solid surface behind her and his own more pointer body in front of her. Sans felt a wall of magic and he could no longer sense that Chara was there; maybe she never was, and both he and Frisk were chasing a false mirror (albeit a very annoyingly solid one when she wanted to be).

And now they were both stuck inside a broom closet.

Like always, he greeted the average every-day shitty situation with an opening punchline.

" _Fancy_ meeting you here."

* * *

Okay, so that definitely could have gone better. The first time in what felt like ages that they were able to speak to each other and he had to go and scare her. Perfect. Good job.

Not like it could've gone any better. As of recently they weren't on the same team anymore, and two ends of a spectrum don't always get along. He knew that already, for a while, it just hurt so much more to _say_ it, as if keeping hush about it would've made the cut any less noticeable. But now there was a solid line, with neither to cross it.

It's for the best, he tells himself, and that's the only thing moving him forward at this point. And through time, maybe, it'll hurt less. But there was something nagging that felt like, whatever amount of time this ball of events Chara had set in motion, there wasn't much of it left.

Speaking of nagging...

"Fuck."

His voice was just barely above a whisper when he spots Undyne on the bathroom floor, his eye leaking blue fire and it took a lot to restrain himself in order to evaluate the damage down on the female monster. The green light of her soul was barely lighting behind one of her eyes; looks like they were matching in that department now, it had taken a while for him to keep his magic from leaking but he was sure Alphys would help to make the recovery faster as she had done with him. If he had any guts he was sure they would clench tight as he felt himself try not to ram his fist on to the floor, his hands kept from trembling as he wiped Undyne's blood from her cheek.

Chara was definitely going to pay for this too, he thought as he prepared to carry his partner's whole weight over his shoulder. She murmured something when he moved her but he ignored it, too _fucking pissed_ _off_ to even care what she has to say. He will be apologizing big time, though, when she regains consciousness, the guilt already setting on his mind.

Sans stops at the sight of something black smeared against the tiles. And when he notices the pool of... ink?... he falters completely, or at least enough for him to feel like he wasn't inhaling brimstone. Everything in his sight had been red, wrath colliding with his soul and making his magic feel unstable by the second, a flash of yellow sputtering out like a flare from cyan flames. But now with the neon light and contrast of what also looked to be black suits on the floor he was, once again, hesitating on what he should do next.

Undyne was in need of medical attention, and he doesn't think she'd make it through a drive, and he for sure did not have the energy to make two trips if he wanted to bring any of this... whatever it is. He had a feeling it might be important though, so he quickly bent down to scoop up a tie and wiped it over the black substance. He grunts then, shifting Undyne again and patting her back. This should be good enough.

"Fuck," he says again, hoping there were no cameras inside the room.

Sans teleports then, moments before Frisk steps inside to see the leftover mess.


	3. identical loss

Anger can be explosive, and a thundering rage could be dangerous. Not very pretty, it got messy, and it was hanging by the thread of the unprofessional. And Sans was the calm type, he'd think he wouldn't blow in an upsetting proportion, that he'd have his emotions under control. Very few got to see how he could really be, when not working. His brother was the default, and Frisk was the only human who managed to warm up to him so quickly. But _Chara_.

She seemed to know how to hit every fucking nonexistent nerve in his body. Crawl her way into his skin, so to speak, and thrive off his pain like some goddamn virus.

So now his temper was not one of a quiet blizzard, more so of a wildfire. And it spread in flashes of blue and yellow. It threw chairs, broke tables, shattered glass windows, bruised and cut flesh. It was loud and destructive and could _not_ have been less professional than this. But _fuck that_ , fuck the quiet, have anyone _dare_ to try to approach them at this moment, he was surely not going to back down and he wasn't sure if he even could at this point.

And Chara made no move to run either, only ever hit back with as much force her human body is able. Being trained and educated, however, made her a difficult opponent. Might he say an _impossible_ one. His brother never had a chance, did he?

 _Sneaky little witch._

Human Determination was enough to deal with as it is without the user being taught magic, but it didn't stop Sans from being reckless. Her knives had slashed as much as her fire had scorched him, some parts of him sliced, other parts charred, and yet still he continued to assault her with furious rows of attacks. Blue magic cheated, made her steps heavier or her hands, sometimes he'd launch her to the walls when she couldn't deflect his hold just in time. She was never one for being defensive and he took advantage of that.

He wasn't being careful though, and she planned this, she must have – she planned to burn that building, have all those documents become crisp and useless, throw the plan in a loop and now there's police on the fucking case and a fire brigade and ambulances and sirens

and fire

and dust

and _she planned this_

– _she murdered him._

The sniper at the window and Chara being the only person residing within the same room spelled it very clear.

A fanged skull in the shape of a wolf's head appeared and he aimed it straight at her. He felt his chest heave, his legs were giving in, and he wondered why the hell he could be so tired when adrenaline should have been keeping him up. And then he remembered.

 _Tea_.

She offered him tea before they all got here. No doubt she'd either drugged it, or better yet poisoned the drink. It was her specialty. He briefly wondered if any of the others were going under the same effects, and his jaw tightened.

"You dirty–"

"I'd be _insane_ ," she interrupted, deep breaths making her voice seem raspy, and she wiped the edge of her mouth, "if I went against you without a trick up my sleeve."

He couldn't feel the same energy from before anymore, though his rage was in tact, but it was useless when he couldn't act at its whim. Sans felt himself shake, wolf skull disappearing with a panicked growl, and then the monster fell to his knees. Summoning his blasters took too much from him in this state, laced with an unknown chemical that would decide if he'd wake up after this or not.

Skeletons don't need air, he didn't have lungs, or heart, no organs. But he understands now the fear some humans have, of feeling like you're drowning. He dug his phalanges into the wooden floor and vaguely heard himself wheeze, his whereabouts suddenly becoming dimmer.

"It won't kill you."

Sans barely has time to register how cold Chara's hands were on his head, fingers sliding to the front of his face and latching inside his sockets to pull him up, then slammed him down skull first. He coughed and tried to spit, but he wouldn't be able to do that anyways. The lights that made up for his eyes were now most certainly gone as well without his magic, so he couldn't exactly glare at her either.

How pathetic he felt at the moment. How destroyed.

"I had to give you an extra dose just in case, and fuse it with magic, obviously, for someone like you."

He didn't want to hear her, even if earlier he'd give it his all just to catch that last rotten breath leave her pale lips as he chocked the life out of her. But she continued talking, a bit rapidly, probably knew she didn't have a lot more time to leave the area, and he wasn't going to stay conscious for everything she had to say.

The red-eyed human raised one more knife, looking at its shine or maybe her reflection, before facing him again, her hand still at his skull, holding him down. Sans couldn't make out anything by then, the light of her skin becoming blurry and her expression hidden in the darkness of the room. He felt his fingers twitch, one last call to his magic, _any_ of it, but not even a fuse.

"Guess I won't feel too bad after this. Seeing as you tried to kill me, so."

 _Hypocrite._

He couldn't utter a single word, only felt steel graze across his left cheek, over his scar-like crack, before stopping at his eye. Then he didn't feel anything else.

* * *

Sans woke up with his wrists zip cuffed over his head, a metal pipe keeping him from slouching down. He felt emptier than usual – _ha_ – and the brow of his sockets melded to a frown. The skeleton monster had his head more clear, logical thoughts residing back into his head where they should belong, and he grunts as he rolls his neck.

There would be no calling of magic for a while, so it seemed. He thinks he'd be more shocked at that, but that sensation had run out. Some of his power lingered, since he was still alive, though how much Chara took made him wonder. And _why_ did she want it? She wasn't completely incompetent at it, for a human, and she had never shown interest in being better.

That really didn't matter, he knew he was trying to distract himself. And it wasn't working.

He hears fast footsteps approaching, passing the room he was in and he didn't bother making a sound. Sans kept his head bowed, looking at the floor as if it provided all of the answers. The footsteps slowed down and retreated back, soon stopping at the door. It creaked open, and a warm presence made him ball his hands into fists whereas it would have usually calmed him amazingly.

But he couldn't feel calm. He was still so, very, angry.

Sans could hear her breathe in, and then her hands were cupping his face, the softness of her skin making the tension all the more unbearable. But Frisk's concern clouded everything else upon seeing the monster this way, and she pressed her forehead against his to catch the glowing orbs in his sockets, but she found nothing there.

He moved his head to the side, away from her direction, her hands sliding away and she sighed quietly. Frisk got up after a moment and observed the room, soon catching the sight of the sniper leaned next to the window. He could feel her anxiety rising as she moved closer.

"Sans," she started with a firm note, but it was crumbling fast. "Where is my–"

"Sorry, honey." His voice his gruff, dry and hoarse, and he didn't mean to sound that way but he was almost uncaring. "Don't really want to talk right now."

Frisk rubs her elbow, her back to him, brown eyes trained on the gun.

"There wasn't any dust."

She was raw determination, and he admires that, but he would really prefer her to stay quiet. He needed the time, the moment to think, not act, to progress information, not move again

even if sometimes the silence made his skull feel on fire

it wasn't

 _reminding him_.

And he really didn't want to have Frisk see him when he has to face the music.

"So he... Papyrus couldn't have–"

His arms moved down, swiftly away from the wall and the pipe holding him captive was torn from its place, meeting the floor with a harsh sound. She had flinched, turning to see the other tear the cuffs apart so easily, then pacing across the room to throw a chair against the door.

" **I said I don't want to talk right now."**

Frisk bites her lip, hand raising up over her mouth as she looked away and to the outside instead; saw the building now like black coal, huge gapes on the sides and windows broken, _a ruin_. A tear runs down as she closes her eyes.

"I'm sorry."

Sans rubs a hand over his face and reaches for that peace of mind again. After that stunt, however, he felt exhaustion keep up with him.

Anger will still persistent in staying.

"I'm sorry."

So did grief. And he didn't want it there inside him any longer, but it wasn't a solid piece of him that he could just rip out.

He felt sick.

"I'm sorry."

"Stop." He swallows, or makes an attempt to, keeping that stubborn ball of frustration and loss held down. But he was weak, and so tired. He's not sure if he was fighting it anymore.

"Sans."

Damn her, she was relentless.

"I don't want... I _can't_."

"It'll help."

She won't give in, and though she continued to push, she was nothing but gentle while doing so. He can't win against her, not with her soul exposed to him like that, coaxing his own to reach out.

"I promise."

 _Well, fuck._

The steps forward felt like lead in his shoes and he was relieved when Frisk closed the rest of the distance for them both, and it was her who caught him, her arms circling around his shoulders as he let himself tumble.

The rest of their team found them a bit later, Frisk cradling Sans, his magic leaking from one socket, both human and monster tormented from an identical loss.


End file.
